How long does a Tesla battery last?

How Long Does a Tesla Battery Last

Let’s understand a few things about Tesla batteries.

Tesla uses standard Panasonic lithium-ion batteries that we use in our daily lives. When the battery is charged, the positive lithium-cobalt electrode gives up some of its lithium ions, which pass through the electrolyte to the negative graphite electrode and stay there. During this process, the battery draws and stores energy.

These batteries are connected in a series and parallel combination that is very internally calculated to provide a balance of longer range and instant torque, performance and longevity. These nearly 7,000 cells are made up of 16 modules that connect together to facilitate any replacement or service that needs to be performed.

The dimensions of these batteries govern the density at which energy can be stored in a given volume of these cells and represent an ideal balance between surface area for cooling, the amount of energy that can be stored in a given volume and most important “price”.

The batteries used are 18650 and 2710 lithium-ion cells. These battery nomenclatures represent the dimensions of the cells, where the cells have stretched the length from 65mm to 70mm and increased the cell diameter from 18mm to 21mm.

How long does a Tesla battery last

Among other unique feats associated with these batteries, a special epoxy seals the battery pack making it difficult to remove, replace and reuse individual cells. A plastic liner was used between the cells to provide structural support to prevent the cells from bumping around in the pack.

The anodes and cathodes of the cells have been significantly improved from 18650s to 2710s, improving battery life and performance. The 2170 design is 46% larger in volume than the 18650 and is able to hold 10-15% more energy.

Tesla was able to pack a comparatively larger surface area of battery material into the 2710 compared to the 18650. This, when added to the improved internal battery design, equates to denser energy in the same volume at a lower weight.

All of these superior components and the advanced battery pack design make up the Energy Storage System (ESS). There are several very important systems built into the ESS that enable it to perform as expected:

  1. Battery Management System (BMS)
  2. Cooling system
  3. Charging station

The Battery Management System

The BMS is a dedicated control unit that watches each cell of the battery pack and works with each one individually to maximize its performance and longevity so that the degradation that occurs over time is carefully controlled. The BMS controls the flow of energy to and from between the battery pack and the electric motors. The BMS can play a key role in increasing the life of Tesla’s battery pack.

Another amazing development is the charging behavior. Lithium-ion batteries are happiest between 30% and 70% state of charge. Cell degradation is rapid when they are charged to 0% and to 100% in any single charge cycle or when they are left plugged in to charge at 100% for additional hours.  Tesla’s instructions recommend a daily number of charges. The AI in the car learns from the user’s usage pattern and suggests to the user the appropriate charging percentage for their optimal driving without overcharging the battery. It suggests that charging above 90% should only be done if you plan to travel long distances and start your journey immediately after reaching 100% charge. All this ensures the good condition of the battery.

The battery of an electric vehicle has a buffer built at the top and bottom end of the battery, which means that a 100% state of charge does not always mean that all the cells of the battery are fully charged, but the cells that are functional are 100% charged. Similarly, the lower part of the battery may be affected by some cells that are inactive and holding a charge, but not usable. This battery gap helps maintain the car’s electrical system if the battery charge is too low, and the buffer system gives the BMS some leeway in estimating the car’s total range.

The Cooling System

An efficient cooling system designed to prevent catastrophic cell failures from spreading to neighboring cells, even when the cooling system is turned off. The cooling system and battery management system maintain temperatures and voltages within specified limits. As battery packs become more compact and store more energy in a smaller volume, their flammability temperature has dropped significantly from about 350 degrees F to about 150 degrees F.

To overcome this serious problem, the current production line uses glycol coolant in the cooling system, which has been replaced by a serpentine cooling system, a much more efficient Manifold cooling system. These cell layout has passages between them through which the glycol coolant is passed effectively decapitating the heat generated, which can reduce performance as well as cause other problems such as overheating or catching fire.

The Charging Station

Since batteries are direct current (DC) devices and home electrical service is AC, home charging typically uses a 240-volt circuit providing 40 amps (10kW of power).  A car equipped with a built-in charging system rectifies the AC current, converting it to DC.  Charging this way usually takes several hours, so Tesla has installed Supercharger DC charging stations around the world that deliver up to about 135kW of power.  DC bypasses the car’s charging circuits and charges the battery directly.  This is much faster, taking between 20 and 40 minutes. Frequent use of charging can accelerate degradation because it can quickly damage the ions required to carry charge in the electrolyte, making some cells obsolete.

Tesla battery life can vary depending on how well each battery is controlled to prevent degradation, which as a whole determines the life of the battery pack.

Battery Degradation

Speaking of battery degradation, the data shows less than 10% degradation in energy density after driving over 160000 miles on Tesla battery packs. The data collected over a period of time shows that for the first 50000 miles the Tesla battery pack loses 5% of its capacity, but after the 50000-mile mark, the capacity evens out and it is observed that it is difficult to make the pack degrade by another 5%.

The data collected suggests that to get close to 90% capacity, the average battery pack can travel over 186,000 miles.

Early indications are that Tesla Model S batteries have only degraded by about 5% after ~30,000 miles (Image: CleanTechnica)

Conclusion:

The warranty states that the battery and drive unit in Tesla vehicles are covered for a period of -.

  • 7210 battery pack (for standard range): 8 years or 100,000 miles, whichever comes first, with a minimum of 70% capacity retention during the warranty period.
  • 18650 battery pack: 8 years or 150000 miles, whichever comes first, with a minimum of 70% capacity retention during the warranty period.
  • 7210 battery (for long range): 8 years or 120000 miles, whichever comes first, with a minimum of 70% capacity retention during the warranty period.

According to commonly accepted data that the average driver drives about 12,000 miles per year, Tesla’s battery life can be assumed to be between 8 and 12 years within the warranty period. Tesla Motors also claims that the current lifetime range of its battery packs is between 300,000 miles and 500,000 miles. Given standard conditions and an annual mileage of 12,000 miles, expect a total lifespan of 25 to 40 years.

Referring to the warranty details and using this data, again assuming standard conditions and annual mileage of 12,000 miles, keeping 70% capacity retention as the limit after which the battery must be replaced, so replacement at this point would take about 15-18 years.

Getting the Show on the Road

There are many rumors and speculations around the topic of battery life of Tesla cars.

We are going to ignore all the nonsense and focus on facts and figures. Some of you may already say, “Wait a minute, after all, this coveted brand doesn’t publish official numbers.” While this is true, many drivers from around the world have released their figures.

The most reliable way to measure longevity is to fully discharge the battery and then raise it to 100%. Tesla owners in most of the available surveys did exactly that.

Their diligence allowed us to see some significant patterns. The key point is not only to calculate maximum life, but also to consider the rate of degradation.

According to European survey reports (from a Dutch-Belgian group of Tesla owners), there is a slight drop in performance after 50,000 miles, but no more than 5%. After 160,000 miles, the battery is running at 90% capacity.

These numbers are much better than those put forth by EV skeptics and cynics.

How Long Does a Tesla Battery Last: Numbers Game

It would be natural to expect that a moment of more aggressive battery degradation is coming.

Some suspected it might happen after 300,000 miles. However, the study mentioned earlier showed that the battery retains 80% of its capacity after 500,000 miles. Over time, the rate of degradation actually decreases, which is great news.

This means that, barring failure, the battery will extend the life of even state-of-the-art internal combustion engines for a long time. To confirm this conclusion, we looked at other studies and anecdotal accounts.

So it’s safe to assume that a 90% battery efficiency should reach up to six figures.

Some of these studies report even more impressive numbers. Tesloop claims a range loss of just 6% after 200,000 miles. There are experts who say it can still run at 85% efficiency after half a million miles.

It should be noted that the Model 3 is unique in that it has a battery degradation guarantee. For a standard battery, it guarantees 70% capacity after 100,000 miles, while the long-range battery has a 120,000-mile guarantee. It’s a slightly more generous Nissan warranty for the Leaf model (66% over 100,000 miles).

When it comes to degradation issues in models like the Model S and Model X, unfortunately you’re on your own.

A Matter of Caveats and Nuances

Keep in mind that averages don’t always translate to individual performance.

It’s not uncommon for a battery to last much less than advertised. No one can completely protect owners from unpleasant surprises. However, data shows that only a small percentage of them (5.6%) experience battery failure.

Another piece of good news is that Tesla guarantees its batteries against failures and defects for a period of 8 years. This means that during this time, the company will repair or replace them free of charge.

Also, it is important to note that some battery packs are more durable than others. Most of the failures are related to the 85 kWh battery packs, which are the longest on the market. On the other hand, the Model S hit the roads in 2012.

We’ll have to wait a bit longer to see how its battery will hold up when covering real-world distances. Nevertheless, so far the available data paints a promising picture. It would be a surprise if it turns out that Tesla has somehow managed to lower the bar.

A Look into the Crystal Ball

In April of this year, Elon Musk announced that the new batteries would be able to last for 500,000 miles.

The body and powertrain will last twice as long, which means only one battery change over the life of the car.

In other words, the improved powertrain should give you at least a couple of decades. What’s more, the company will provide battery module replacements for between $5,000 and $7,000.

Skeptics are not so convinced. They believe that these claims are more on the optimistic side. Even if this turns out to be true, we rightly expect to see a significant improvement.

Of course, we should be honest and say that not everything is the fault or merit of the manufacturer.

In all likelihood, charging habits have an impact on the rate of deterioration. Tesla has stated on one occasion that consistent charging harms battery health.

Environmental factors should also not be overlooked. Extreme heat, for example, is the bane of any electric battery. Other factors that play a role are average speed and frequency of fast charging.

Despite these obstacles, however, Tesla cars are a fairly cost-effective proposition. You should be able to enjoy many carefree hours behind the wheel. By the way, you’re contributing to the environment.

And since fossil fuels are running out, you may want to switch to electric vehicles sooner rather than later.

Electric Dreams Do Come True

The era of electric cars has arrived.

Despite all the hype and enthusiasm, many drivers still worry that the battery may die prematurely. There are also many concerns about the loss of battery capacity.

Well, various data sources have come together pretty well. They dispel the uncertainty surrounding the question “How long does a Tesla battery last?”

As it turns out, most suspicions are misplaced. The Tesla has a well-designed battery pack, built to last. Its performance also degrades slowly, over thousands of miles.

Malfunctions and failures are fairly rare.

For all these reasons, the present and future look bright for Tesla and its customers. We live in a time where technology is making more and more advances. Breakthrough innovations are just around the corner.

Take a look at our green living section to learn more about going green. It’s time to become a sustainability champion!

Battery longevity

First, let’s address a statement you often hear: “replacing your batteries in a few years will cost you thousands”. This statement seems to be true. We’ve all had first-hand experience with something like a smartphone that doesn’t hold a charge after a few years. Or a laptop that you can’t use for more than a few minutes before you have to plug it back in to charge.

A phone has a lithium-ion battery. An electric car has a lithium-ion battery. So it must be true that the EV battery will be pretty worthless after a few years, just like in your smartphone. The problem is that correlation does not imply causation. Humans are natural pattern recognition machines, so we are prone to finding observable connections between things when that connection is not actually there…. or in this case… it is simply misunderstood.

I have made available some videos on battery technology and the research that is currently being done. I’ll provide some links in the description if you want to see more, but there are some pretty big differences between the battery in a phone and the battery pack in an electric car.

The first major difference is the number of batteries we’re talking about. In a smartphone, you have one single lithium-ion battery. An electric car is made up of many small batteries combined into a single pack. In a Tesla Model 3 with standard range, there are 2,976 individual cells. The long-range battery pack consists of 4,416 individual cells 1 that are arranged in rows with an advanced battery management system that controls charging, discharging, and temperatures. The system manages the individual cells to maximize their performance and life, so degradation that occurs over time is carefully controlled. This is very different from a single cell in a smartphone.

The second major difference is the charging method. How many of you plug your phone in at night when you go to bed, and then unplug it in the morning when you wake up and go to work? And then occasionally plugs in your phone at work or during your car commute? Lithium-ion batteries are happiest when you use them at between 30% and 70% charge. It’s harder on the battery when you drain it to zero and charge it to 100%. So constantly driving your phone’s battery to 100%, as well as leaving it plugged in at 100% for extended periods of time, will actually accelerate battery degradation. Manufacturers have been implementing battery management systems to help combat this problem, as in Apple’s iOS 13 update. The system learns over time when you typically get up in the morning. It will charge your iPhone to 80% overnight, and wait until it’s charged to 100% shortly before you usually get out of bed. 2 Systems like this can help reduce the strain on your battery and extend its life.

Electric cars, such as the Tesla Model 3, also recommend a daily charging rate. When you plug in the car, Tesla’s user interface will show you the recommended daily charging range, and it will also make it clear that going over 90% should only happen on longer trips. As soon as you hit 100%, you should start your journey immediately. Keeping your daily charging routine below 90% helps keep your battery healthy.

Here are some study results that showed how charging behavior affects lithium-ion battery life. 3

Battery degradation study

The Y-axis represents the total available charge capacity, and the X-axis represents the number of charge cycles. Batteries that charged to 100% and drained to different states of charge performed worse than batteries that charged to 75% or 85% before draining. To make this very clear, let’s compare the two data points in the graph. Both of them used 50% of the battery capacity each cycle, but one charged to 100% and the other charged to 75%. After 1000 cycles of 100%, the battery was at just over 90% of its original capacity. Expand that and the gap widens after thousands of charge cycles.

And finally, the EV battery pack typically has a buffer built into the top and bottom ends of the battery. This means that the 100% displayed by the car is probably not the actual 100% of the battery. The same goes for discharging to 0%. There is wiggle room in the battery to keep cars electric systems running if the battery is running too low. This buffer gives the car’s battery management system some leeway in estimating the car’s total range. In some cases, you can eat into this buffer slowly over time so that the car’s driving range appears unchanged. 4 It’s not clear if Tesla does this or how much, but there may be some leeway there.

All this proves is that you can’t equate phone battery life with what you would expect from car battery life.

Battery degradation – by the numbers

So let’s take a look at the data that Ramin, the creator of Stats, put together to see how Tesla Model 3 batteries are doing. Looking at the 15,000 or so Stats battery range data points, there are some pretty clear trends taking shape. If you look at the median range reported for the long range rear-drive Model 3, you can see a rapid drop in range over the first 15,000 miles and then it starts to level off a bit. This corresponds to what we saw with the Model S, which also slows degradation as more miles are accumulated. This is a non-linear form of degradation. 5

If we assume that the average driver drives about 12,000 miles per year, then in the first year, the range may decrease from 324 to 313 miles, or 3.4%. In the second year, it goes from 313 to 308, a decrease of 1.6% the following year. The long range AWD Model 3 shows similar declines; going from 310 to 301 in the first 12,000 miles, which is about a 2.9% drop. And like the RWD Model 3, AWD drops 1.6% after 12,000 miles.

Stats Median

Tesla warrants its long-range batteries for 8 years or 120,000 miles at 70% of original charge. 6 That means a 310-mile, AWD, long-range battery pack could potentially be about 217 miles of range after 8 years in a worst-case scenario. Breaking that down by the rate of degradation from year to year, you’re looking at a loss of 11.6 miles per year. But as you can see from the data, Tesla, like any other warranty company, is relying on the worst case scenario … and how much to drive. A 12,000-mile-per-year driver might see an 11-mile drop on the long-range RWD Model 3 in Year 1, but only a 5-mile drop the following year. The long-term degradation should, if consistent with what we’ve seen in the Model S and X, be well over 70% of the original charge in 10 years for the average driver who drives 12,000 miles per year.

We can also look at the data in a broader perspective to see the full range of reported ranges for each 1,000 miles driven. If you’ve never seen a violin chart before, it helps illustrate the spread and concentration in each bucket. Each curve is basically a tiny bell curve on its side. Most people will fall in the center of the curve where it is highest, which is also where the median falls. The lowest points of the curve are the outliers, which are less common, but can still be experienced by a few of you out there. I myself am one of the outliers in this data.

There is a lot to take in looking at this type of view, but there was something that jumped out at me from the distribution. There’s a lot of variation in the estimated range in the spread from group to group, but there’s a big wrinkle to keep in mind with the estimated range: it’s the estimate. 7 And that estimate, which is generated by the battery management system, can lose calibration with the true maximum capacity of the battery. If you charge to 80% every day, there may be a slight drift in this estimate, which can be offset by charging to 90% or full on a long trip. Software updates that are pushed out to the car can reset some of these estimates, which can also contribute to why you see them fluctuate up or down at times. I have observed this myself. After the v10 version was released, my rated range started climbing back up. Charging and driving habits, like not charging daily or driving daily, may play a role in these degradation numbers looking high even though their battery health is fine.

Ramin recently released a new app, Battery Compare, where you can plug in your nominal range, current charge percentage, and odometer to see where your car falls in the data I shared in the video. Looking at my car, I am falling outside the norm, on the low end, for cars that fit my criteria. I pay attention to this, but I don’t worry about it.

As electric car owners, we need to look beyond the small fluctuations we may see in our nominal range and keep an eye on the long-term picture. Follow charging and usage best practices, such as charging to 80% or 90% each day. Only charge to 100% for longer trips and start driving as close to reaching 100% as possible. Just as I showed in the data, when you look long term, you should see something small like a 4-5% drop in the first 24,000 miles.

EVs are still relatively new to many people, so there is a lot of fear, uncertainty and doubt out there. It’s easy to jump to conclusions based on limited experience and believe some of the misinformation that’s out there. But even EV owners like me can get caught up in range anxiety and be very vigilant about tracking the estimated range of our batteries. Any small drop can make us worry and fret about how long our car will last. Finally, after reading these numbers and doing a little research: just relax and enjoy your car.